Necromass as seed reservoir in macroforb meadows with varied moisture conditions

Abstract

Necromass, i.e., dead plant parts, has a great impact on the spatial patterns of populations and communities. Depending on its thickness and the degree of decomposition, it may constitute a space-blocking physical barrier and impede recruitment of individuals due to, e.g., autotoxication. The aim of the study was to determine the role of the necromass layer in formation of the soil seed bank of variously moist meadow communities and its influence on the efficiency of generative reproduction. The authors paid special attention to the possibility of capture and storage of seeds of species occurring in the vegetation cover by necromass. Additionally, selected features of seeds of species present on the necromass were analyzed in order to identify species that can potentially contribute to formation of the necromass seed bank. The plant cover comprised 52 species in total. Seedlings of 21 taxa appeared on the necromass and their number ranged from 10 to 13, depending on the patch. The density of the seedlings ranged from 339 to 4923 m−2. In all patches, Lythrum salicaria and Lysimachia vulgaris seedlings were most numerous. These two species were characterized by the highest frequency as well. The low values of Jaccard’s index (0.28–0.36) imply a low share of taxa that are common for the necromass and the vegetation cover. This result should be explained by the occurrence of large disproportions in the number of all species identified on the necromass and among the vegetation. The seeds are typically characterized by small sizes and usually have smooth or finely striated and/or ribbed surface texture. The presence of additional structures, e.g., pappus and hairs, in the largest and heaviest seeds (Crepis paludosa, Geum rivale, and Cirsium spp.) may help seeds capture in the necromass.

Keywords

• macroforb meadow
• necromass
• seed bank
• seedlings emergence
• vegetation